Switching amplifiers yield high outputs at high efficiency. In that most effect control through modulation of the duration and/or frequency of output pulses, however, their resolution is typically inversely proportional to bandwidth. This is due to finite switching speed limitations of the circuitry involved. Resultantly, switching amplifiers have earned a reputation of high distortion, and often are relegated to low bandwidth or imprecise applications. Improvement of the resolution of these amplifiers will open many applications for them previously reserved for their less-efficient analog counterparts.
This invention resides in circuitry and methods of increasing the resolution of a switching amplifier. It has been found that accurate production of pulse widths approaching zero is the prime resolution-limiting factor of some switching amplifier topologies. This particular limitation results in very audible crossover distortion. The technique disclosed herein is particularly helpful in this instance, in that its activity opposes the existing amplifier output, balancing the composite output.
Operation of the inventive circuitry broadly relies upon selectively diverting a controlled portion of the output voltage, current, charge, or power from the load, the resolution of which is inversely proportional to the portion diverted. Although modulation of the diverted voltage or current may be effected by pulsewidth variance, analog modulation of voltage or current diversion may alternatively be utilized.
Although current amplifiers are discussed for sake of simplicity, the technique is equally applicable to both voltage and current amplifiers. Multiple instances of the invention may also be scaled at contiguous resolutions to yield greatly improved system resolution.